Various kinds and sizes of particulate abrasive delivery tools have been proposed in the past, including portable assemblies incorporating an abrasive hopper, a nozzle and a trigger for initiating the delivery of the abrasive stream, such as U.S. Pat. Nos. 4,941,298, 4,628,644, 3,163,963 and 2,133,149. However, each of these assemblies requires the addition of a remote source of compressed air or other pressurized driving gas to actuate the device.
Other proposals employ separate or remote hoppers of abrasive particles, such as U.S. Pat. Nos. 4,090,334 and 4,674,239, but again, these patents also employ remote sources of compressed air as the source of the driving fluid. German patent publication DE 3624023 Al proposes several different “portable sandblaster” devices incorporating a container of compressed propellant gas, but these proposals lack valuable features and important advantages of the present invention.
Additional hand held sandblasting devices such as those described in U.S. Pat. Nos. 5,514,026 and 5,181,349 also have a refillable hopper, which is attached to a pressurized propellant source which when operating allows pressure into and up one of two delivery conduits into a venture chamber, so that when operating, it will cause aspiration in which an additional conduit delivers abrasive particles into the mixing chamber and outward through a nozzle towards an intended target. This type of operational method of a sandblaster is very inefficient, as a majority of the device's pressure is used to generate the venture in the nozzle's chamber to aspirate abrasive material into the ventures via a pickup conduit into this chamber, where it is mixed with pressure blown out of the exiting nozzle with little strength.